The present invention relates to a method for the purification of rabic virus, and particularly to such method for obtaining effective vaccines against rabies.
Rabies is a disease occuring almost all over the world, particularly in Asian and African countries. This disease is caused by rabic virus, which is known to be a bullet-shaped RNA virus belonging to Rhabdoviridae measuring about 180 nm in length and about 80 nm in diameter. The virus is infective to mammalian animals. Thus, rabies is mediated even through wild animals such as bats, foxes, weasels etc. as well as dogs. Affliction with rabies occurs upon the invasion of rabic virus into the central nervous system through peripheral nerves and is tranmitted from an animal infected with the virus by biting or licking. The mortality rate in human patients approaches almost 100 percent.
The only possible way for preventing and curing such horrible disease is a vaccination, in which a highly purified vaccine is desired to be used.
A typical conventional method for the production of a rabies vaccine, particularly for animals, includes the step of preparing a rabic virus-containing material by propagating rabies virus infected into the brains of mice or any other appropriate animals and harvesting the propagated virus from the brains and the step of refining or purifying the harvested material by means of centrifugation and/or chemical treatments with such agent as sodium carboxymethyl cellulose, followed by an inactivation treatment. More recently, particularly in the case of production of rabies vaccine for human beings, tissue-culture types of rabies vaccines have been developed in which there is used such cell as cultured chick embryo cell. This type of vaccine is more effective and safe because there are contained the less contaminants as would orginate from the brain substances. A typical dried inactivated tissue culture rabies vaccine of such type is prepared as follows: ##STR1##
However, the conventional methods for preparing rabies vaccine, including the one as illustrated by the above flow diagram, require sophisticated and costly techniques, such as ultrafiltration and ultrahigh-speed centrifugation, to purify rabic virus and only produce vaccines of low purities.